The present invention relates to a sheet collecting apparatus and collecting method of the apparatus for bearing and storing sheets carried out of a sheet discharge outlet in a post-processing apparatus, an image formation apparatus, etc. and more particularly, to improvements in an aligning mechanism and aligning method for neatly positioning and storing sheets fed onto tray means.
Generally, this type of sheet collecting apparatus has widely been known as an apparatus for bearing and storing sheets fed to a sheet discharge outlet of an image formation apparatus, etc. For example, post-processing apparatuses are known which have a post-processing unit for temporarily bearing sheets from the sheet discharge outlet to collate for each set, and performing post-processing such as binding processing, folding processing and punching processing on a bunch of sheets, and collect sheets with images formed for each set to perform bookbinding stapling, punching filing holes and the like.
As such a sheet collecting apparatus, conventionally, for example, Japanese Laid-Open Patent Publication No. 2006-248686 [Patent Document 1] discloses in FIG. 3 an apparatus where a processing tray is disposed on the downstream side of the sheet discharge outlet, and a sheet from the sheet discharge outlet is switched back to the tray and loaded and stored. Then, a collection structure is proposed where the post-processing means such as stapling binding is disposed in the rear end portion of the tray, and in switching the sheet back to store, the sheet is forced to strike a regulation stopper disposed in the tray rear end portion to be aligned.
When a sheet is loaded on the tray from the sheet discharge outlet as described, Patent Document 1 as described above discloses a method where a forward/backward rotation roller is disposed above the tray to be able to move up and down, the roller moves downward to transport a sheet in the sheet discharge direction after the sheet front end enters onto the tray, and next, in the stage where the sheet rear end enters onto the tray, the roller is rotated backward to switch the sheet back to transport.
When a sheet fed from the sheet discharge outlet is thus moved forward on the tray, and then, moved backward to strike the stopper to be aligned, the uppermost sheet already stored on the tray sometimes interferes with alignment of the transported sheet. The interference phenomenon of the uppermost sheet will be described based on FIG. 9. In FIG. 9, in loading and storing a sheet from a sheet discharge outlet 90 on a tray 91, a forward/backward rotation roller 92 is disposed above the tray to be able to move up and down, the forward/backward rotation roller 92 moves down to an operating position to move the sheet forward in the sheet discharge direction in the stage where the sheet front end enters onto the tray from the sheet discharge outlet 90, and after the rear end of the sheet enters onto the tray 91, the forward/backward rotation roller 92 is rotated reversely to cause the sheet rear end to strike a rear-end regulation stopper 93 to align. In such a conventional structure, the uppermost sheet Su stored on the tray is fed together by the backward action of the transported sheet caused by backward rotation of the forward/backward rotation roller 92, and the sheet rear end is sometimes curved and becomes deformed as shown in FIG. 9.
Thus, when the uppermost sheet is curved, becomes deformed and raised, the front end of the transported sheet cannot enter between a sheet-surface pressing guide 94 disposed in front of the rear-end regulation stopper 93 and the uppermost sheet, and a sheet jam occurs, or the front end is folded when entering the sheet-surface pressing guide 94. The sheet-surface pressing guide 94 presses the sheet by an appropriate pressing force and prevents the curled sheet from rising, in causing the sheet end to strike the rear-end regulation stopper 93 to align. Therefore, the sheet-surface pressing guide 94 is required to meet conditions that the guide 94 allows the front end of the transported sheet to enter easily, and after the sheet enters, presses the sheet end edge by an appropriate pressing force. Then, as the conditions of the guide, it is preferable that the pressing force varies significantly with the load amount of sheets on the tray.
The inventor of the invention reached noting that in reversing forward and backward the transport direction of a sheet to load and store on the tray to push against the regulation stopper to align, the sheet fed onto the tray causes the already loaded uppermost sheet to be fed together, and that double feeding of the uppermost sheet affects alignment of sheets.
It is an object of the invention to provide a sheet collecting apparatus for enabling sheets to be loaded and stored in a neatly aligned state with respect to a regulation stopper disposed in a tray when loading and storing the sheets on the tray. Further, it is another object of the invention to provide a sheet collecting apparatus without a sheet jam occurring due to a sheet pressing guide when a sheet carried onto the tray strikes the regulation stopper to be aligned in a curl corrected attitude by the sheet pressing guide.